hyperons at the PANDA experiment at FAIR Karin Schnning Start - - PowerPoint PPT Presentation
Time-based reconstruction of hyperons at the PANDA experiment at FAIR Karin Schnning Start seminar of Jenny Regina Uppsala, June 21st, 2018 1 Outline Prologue Why hyperons? Hyperon physics with PANDA Challenges with hyperons
Karin Schönning Start seminar of Jenny Regina Uppsala, June 21st, 2018
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Missing in the Standard Model of particle physics: A complete understanding of the strong interaction.
successfully tested.
pQCD fails, no analytical solution possible.
Many fundamental puzzles manifest in the nucleon:
– Its abundance – Its mass – Its spin – It radius – Its inner structure
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Abundance: matter-antimatter / nucleon-antinucleon asymmetry of the Universe. Equal amounts in Big Bang (?) → Where did the anti-nucleons go? Baryogenesis*: possible if
equilibrium.
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*A. D. Sakharov, JETP 5 (1967) 24-27
Picture from Virginia Tech
Mass:
→ 99% of the visible mass in the Universe is dynamically generated by the strong interaction! But how?
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Spin:
spin*.
– Sea quarks? – Gluons? – Relative angular momentum?
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*C. A. Aidala et al., RMP 85 (2013) 655-691.
Radius: measured in – Electron-nucleon scattering – Electronic hydrogen spectrum – Muonic hydrogen spectrum. Results disagree.* Inner structure: – Neutron charge distribution intruguing.**
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*R. Pohl, Nature 466 (2010)7303, 213-216. ** G. A. Miller, PRL 99 (2007) 112001.
When you don’t understand a system, you can* – Scatter on it – Excite it – Replace one of the building blocks
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*C. Granados et al., EPJA 53 (2017) 117
What happens if we replace one of the light quarks in the proton with one - or many - heavier quark(s)?
proton
Λ Σ0 Ξ- Ω-
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– Scale: ms ≈ 100 MeV ~ ΛQCD≈ 200 MeV. – Relevant degrees of freedom? – Probes QCD in the confinement domain.
– Scale: mc ≈ 1300 MeV. – Quarks and gluons more relevant. – Probes QCD just below pQCD.
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Traceable spin: Polarization experimentally accessible by the weak, parity violating decay:
Example: Angular distribution of Λ→pπ- decay I(cosθp) = N(1+αPΛ cosθp) PΛ : polarisation α = 0.64 asymmetry parameter
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Hyperons as diagnostic tool
PANDA Topic Nucleon mass Nucleon spin Nucleon structure Matter-antimatter asymmetry Hyperon production Hyperon spectroscopy Hyperon structure Hyperon decays Key questions
Spin observables sensitive to the interaction process.
𝑍𝑍 based on potential models obtained with ҧ 𝑞𝑞 → ത 𝑍𝑍 data.*
→ Understanding ത 𝑍𝑍 interaction important!
*PLB 761(2016) 456 BaBar: PRD 76 (2007) 092006 ***BES III: Talk by C. Li, BEACH2018
Facility for Antiproton and Ion Research
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The High Energy Storage Ring (HESR)
1.5 GeV/c < ppbar < 15 GeV/c
– Cluster jet and pellet ( ҧ 𝑞𝑞) – Foils ( ҧ 𝑞𝐵)
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with software trigger
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PANDA will use an entirely software-based data selection!
Algorithms will depend on event topology
Weak decays → displaced vertices – Tracks do not come from the interaction point. – Hyperons may miss fast detectors. – Complicated event topology.
Need a data selection scheme compatible with the complex hyperon topology – Independent of track origin. – Dynamic event and track reconstruction. – Paradigm changing event filter concept. – Which detectors are the key players?
New Memorandum of Understanding between PANDA and HADES!
PANDA@FAIR!
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hyperons – 𝑍
𝐵 → 𝑍 𝐶𝛿 (mainly 𝛿Λ quasi-final states)
– 𝑍
𝐵 → 𝑍 𝐶𝑓+𝑓− (mainly 𝑓+𝑓−Λ quasi-final states)
– 𝑍
𝐵 → 𝑍 𝐶𝛿π
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(lack of) understanding of the nucleon.
hyperons!
strong interaction.
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challenging task!
PANDA detector.
– Can be used online. – Is independent of the interaction point.
– Test tools and methods developed for PANDA – Do interesting hyperon physics before PANDA@FAIR.
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